Salvage my summer...I have been struggling with the operation of my Mastercraft all summer. This otherwise reliable boat hasn't run well all year. Boat is 20 years old but only 300 babied hours...

The problem: Flooding, fouling plugs, backfiring, struggling to exceed 200 RPM's, excessive fuel consumption....but all of this only occurs after 20 to 30 minutes of operation.

I have; changed the plugs, fuel filter (twice), replaced the coolant temperature sensor, thermostat, and impeller. All gauges read as they always have --year after year.

Oil pressure is good, temperature is about 135 degrees, I can almost watch the fuel gauge lower!!

I've read a million threads, (most of which are above my level of knowledge). One I just read talked about injectors dumping so much fuel into the cylinder that the oil has been contaminated. When I checked the oil, after limping back to the dock, at a maximum of 2000 rpm's, I was surprised to see it appeared over full.

Suggestions????

mikeg205

09-02-2013, 05:30 PM

Take a video of your injectors firing while this is going on...- 135 is way low... 145 is the minimum it should be...

JimN and CantRepeat will have some good suggestions...

diceman55

09-02-2013, 06:45 PM

Stupid question, but should I take off the spark arrestor and simply video the injectors?

On the temperature...I have owned this boat since 1996. I had 12 hours when I bought it. This is the first season it has given me ANY problems. Thinking that the EFi was sensing that the temperature was cool one thread suggested changing the thermostat. I ordered a new stat from the MAstercraft dealer. I think it is a 139 degree unit. Anyway, when I opened the thermostat housing I found there wasn't a thermostat in the housing. Apparently there never was one.

Suggestions? This problem was occuring before I added the thermostat.

mikeg205

09-02-2013, 07:19 PM

take off the spark arrestor... no t-stat would explain the 135...

diceman55

09-03-2013, 08:52 AM

Maybe I didn't explain this well. There apparently has never been a t-stat, until I installed one last week. I bought one from Mastercraft that I think is a 140 degree unit. I selected that one based on one of the threads on this site. Curiously enough this engine performed flawlessly since I bought it in 1996, until this year. In 2010 we skied every day from May to October 10.